The widespread availability of personal computers at low cost has led to a situation where the public demands access to the Internet and other computer networks at the lowest possible cost. This demand is being transferred to the need to also provide network access for portable devices such as laptop computers, personal digital assistants, and the like. Users of such portable devices even now expect to be able to access such computer networks with the same convenience that they have grown accustomed to when using wire line connections.
Unfortunately, there is still no widely available satisfactory solution for providing low cost wireless access to the Internet at high speed. At the present time, the users of wireless modems that operate with the existing cellular telephone network often experience a difficult time when trying to, for example, view Web pages. This is at least in part due to the fact that the architecture of cellular telephone networks was originally designed to support voice communication and not the packet-oriented data communication protocols in use for the Internet. In addition, the protocols used for connecting users of wide area networks do not lend themselves to efficient transmission over wireless interfaces.
Certain protocols have been proposed that provide multiple data links over a wireless communication system such as one that uses code division multiple access (CDMA). For example, one such system was described in our co-pending United States patent application entitled “A Protocol Conversion and Bandwidth Reduction Technique Providing Multiple nB+D ISDN Basic Rate Interface Links Over a Wireless Code Division Multiple Access Communication System,” Ser. No. 08/992,759 filed Dec. 17, 1997 and assigned to Tantivy Communications, Inc., the assignee of the present application. With such techniques, high speed data service can be provided over digital cellular connections through a more efficient allocation of access to the wireless channels. In particular, a number of sub-channels are defined within a standard CDMA channel bandwidth, such as by assigning a different code to each sub-channel. The instantaneous bandwidth needs of a given connection are then met by dynamically allocating multiple sub-channels on an as-needed basis for each session. For example, sub-channels can be granted during times when the subscriber bandwidth requirements are relatively high, such as when downloading Web pages. The bandwidth is then released during times when the content is relatively light, such as when the user is reading a previously downloaded Web page.
However, to implement such a system requires careful planning of various modulation and coding schemes in order to accomplish the maximum possible bit rate while minimizing the effects of noise, multipath, and other sources of errors. For example, modulation codes and pseudorandom spreading codes must be carefully selected to minimize interference among channels occupying the same radio frequency carrier. In addition, it is necessary for framing bits to be inserted in data streams so that higher layered data protocols such as transmission control protocol/Internet protocol (TCP/IP) communication can take place.